sudo systemctl start minecraft.service
dom@mc_server:/opt/minecraft$ systemctl status minecraft.service
● minecraft.service - Start Minecraft
   Loaded: loaded (/etc/systemd/system/minecraft.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Tue 2019-07-16 19:00:41 UTC; 10s ago
  Process: 2459 ExecStart=/usr/bin/java java -jar /opt/minecraft/forge-1.12.2-14.23.5.2838-universal.jar nogui (code=exited, status=1/FAILURE)
 Main PID: 2459 (code=exited, status=1/FAILURE)

Jul 16 19:00:40 mc_server systemd[1]: Started Start Minecraft.
Jul 16 19:00:41 mc_server java[2459]: Fehler: Hauptklasse java konnte nicht gefunden oder geladen werden
Jul 16 19:00:41 mc_server systemd[1]: minecraft.service: Main process exited, code=exited, status=1/FAILURE
Jul 16 19:00:41 mc_server systemd[1]: minecraft.service: Failed with result 'exit-code'.